Method of making paper-machine felt



United States Patent METHQD 9F MAKING PAPER-MAQHENE Thomas Hindle and Edward Race, Blackburn, England,

assigncrs to Scapa Dryers Ltd, a company of Great Britain, Northern lreland, and the Isle of Man NoDrawing. Griginal application Aug. 8, 1966, Ser. No.

47,956. Divided and this application June it), 19:33,

Ser. No. 289,381

'11 Claims. (til. 28--73) This invention pertains to woven textile fabrics, in particular to a novel method of manufacturing fabric useful as a paper-machine felt such as is employed in the manufacture of pulp, paper, board, asbestos-cement sheets, pipes and similar or related products, the present application being a division of the copending application for Letters Patent, Serial No. 47,956, filed August 8, 1960, by Thomas I-Iindle and Edward Race.

According to customary, prior practice, these felts were manufactured entirely from wool yarns, or, particularly in the case of the felts used in the production of asbestos-cement products, from a combination of wool and cotton. With the advent of nylon, polyester and similar synthetic fibres, it was found that by manufacturing the felt from yarns composed of blends of wool fibres and synthetic fibres, the abrasion-resistance of the felts was greatly improved and the felts exhibited a longer service life.

Whenever a paper-machine felt is composed entirely of wool or a mixture of wool and synthetic fibres, milling or fulling is an essential operation in the manufacture of the felt. Thereby, the weave structure of the felt, which otherwise would mark the paper, is masked at the surface by the matted or felted wool fibres and yet its permeability to water remains of a high order.

Since conventional synthetic fibres do not possess the felting characteristics of most fibres, it was thought essential until recently that the proportion of synthetic fibres incorporated in a woven felt must be less than that which would prevent appreciable milling or fulling of the felt. However, it has been discovered recently that if such a felt, made wholly or predominantly of synthetic fibres, has one or both of its surfaces raised, as by napping or gigging, and the raised fabric is subjected to a process of needling, the surface texture of the resultant fabric simulates closely enough to that of a milled felt made wholly or predominantly of wool to be used as a paper-machine felt. The operation of needling is effected in any known manner, as by passing the woven fabric through a machine wherein the surface of the fabric is frequently pierced by barbed needles, the result being to force the nap fibre-s constituting the raised surface into the body of the fabric.

Unfortunately, in many instances, prolonged needling is required in order effectively to entangle the raised fibres into the woven body of the fabric. Two major defects are liable to arise as a result of the prolonged needling operation. Firstly, serious reduction in the water permeability of the felt is possible, and it is not unusual for the water permeability of the felt after extensive needling to be only one-half of its initial value. This reduction in permeability has an adverse effect on the rate of drainage of water from the paper sheet through the felt when the latter is in operation on the paper-machine. Secondly, the process of prolonged needling the raised, woven fabric breaks many of the fibres both of the raised surface and of the yarns in the body of the felt. This weakens the fabric and makes it more susceptible to degradation by mechanical abrasion.

The expression endless woven fabric as used herein, is intended to include not only fabric which is woven endless initially (the weft in the loom becoming the warp in the finished fabric), but also a length of fabric, woven 3,l?fi,375 l atented Apr. 6, 1965 flat, whose ends have been joined, and wherein the warps and wefts of the fabric are the loom warps and weft-s. In this specification by the term warp is, therefore, meant those yarns arranged in the longitudinal direction of the endless finished product (regardless of how produced), such as a papermakersdryer felt and by the term wef is meant those yarns arranged in a direction which is transverse of the length of the finished product. The synthetic content of the yarns may be in the form of a plurality of continuous filaments, or staple fibres thereof, and general references to synthetic fibres of fibres when they occur herein and in the claims hereof are intended to include, Within their scope, both forms.

In felting wool, adjacent fibres become entangled one with another, and not only do fibres Within the same yarn become entangled, but the surface fibres of one yarn become entangled with the surface fibres of adjacent yarns running parallel and with the surface fibres of yarns crossing one another. Thus, in wool felting, adjacent fibres become attached to one another, and yarns are likewise attached to each other at their crossing points. Broadly stated, the objects of the present invention provide a method of making a felt which has the wear resistance attributable to the incorporated synthetic but which also predominantly synthetic possesses the desirable characteristics of a felted wool felt.

In accordance with the method of the present invention the synthetic fibres and crossing yarns are joined together by integral bonds of the material of which they are composed.

A further object of the present invention is to provide a novel method of producing an adequately water-pervious Woven fabric, for use as a paper-machine felt, which is wholly or predominantly of synthetic fibre and which has not been subjected to a needling or equivalent operation. Another object is to provide a method of making woven textile fabric sufficiently pervious to the passage of water and sutficiently flexible to function satisfactorily as a paper-machine felt and which consists, at least predominantly, of synthetic fibres and wherein, wherever constituent synthetic fibres touch one another, they are bonded together at their mutual points of contact, with the result that synthetic warp and weft yarns, whatever their individual character, become bonded together at their crossing points.

A further object is to provide a novel method of making woven textile fabric, sufliciently water-pervious to constitute a satisfactory paper-machine felt and which consists, at least predominantly, of synthetic fibres, which, comprises the step, after weaving, of so treating the fabric as integrally to bond adjacent synthetic fibres at their crossing points.

A further object is to provide a novel method of making a woven textile fabric, adequately Water-pervious for use as a paper-machine felt and which consists, at least predominantly, of synthetic fibres, which comprises so treating the fabric, after weaving, with a fluid reagent which acts preferentially at the points at which the fibres cross one another, as to cause the fibres to coalesce at said points to form integral bonds.

Briefiy stated the invention provides a novel method comprising as steps; providing a fabric wherein warps and wefts, predominantly of synthetic fibrous material, are so interwoven as to form a structure acceptable for use as the base fabric of a paper-machine felt, and thereafter subjecting said fabric to the action of a chemical reagent which causes some, at least, of the constituent synthetic fibres to coalesce at their mutual points of contact, whereby said contacting fibres are integrally and permanently bonded together. More specifically, the preferred method employs as a reagent an aqueous solution of reactant salt can of an inorganic salt which, in Concentrated form, acts on some, at least, of the synthetic fibres to gel them so as to cause contacting fibres to coalesce and form integral bonds at. their mutual points ofcontact, and thereafter a h ng he br remo esaltr n y h e te'rial.

Preferably the aqueous solution is caused to concentrate I and to localize preferentially in the region of said points of contact, after application .to the fabric.

In the case of fabrics made'wholly orpredominantly of nylon, which is a'polyamide fibre, and/ or acrylic fibres, such as Orlon' (a registered trademark, the property. of E. I. du Pont de Nemours &Co.) or Courtelle (a registerjed trademark, the property of Courtaulds Ltd), (both being acrylic fibres. such as those made of polyacrylonitrile and copolymers thereof), suitable salts are calcium and lithium bromides and calcium. and magnesium thiocyanates- In thecase of fabrics made wholly orrpredomh nantly of. polyester fibres, such asqTerylerie '(a lfQglSiIQd trademark,'the property of Imperial Chemical Industries Ltd); or Dacron (a registered trademark, the property of E. I. du Pont de Nemours & Co.), or containing a material proportion of such fibres in addition to. acrylic and/orpolyamide fibres, suitable salts are calcium and magnesium thiocyanates. In applying the invention, a woven fabric, made wholly out hereinbefore, the general. references to 'synthetic' fibres and fibres herein and' in the claims, are not intended to be limited to the fibres of such yarns. For example, the warpyarns may be spun from crimped synthetic fibres, or from straight synthetic staple fibresQor may becontinuous filament synthetic yarns, or continuous filament bulked synthetic yarns ofthe non-stretch type, such as Taslan-textured yarns, or yarns composed of a a core 'of continuous filament synthetic yarns around which is wrapped a finer'Taslan-textured yarn. (Taslan is a trademark registeredby E. 1 duPont' de Nemours & Co.). The weft yarns are preferably spun from synthetic staple fibres, but these staple fibres may be the commercially-produced crimped synthetic fibres, or theyjmay be prepared'by cutting into staplelfibre length those commercially-producedJcontinuous filament yarns which are known as bulked yarns and s'tr'etch yarns and bulked V and stretch yarns.

or predominantly of synthetic fibres and suitable for use as a, paper-machine or like felt, is impregnated" with ,an' aqueous solution of the selected saltand 'the water is evaporated from the fabric 'so that the salt s'olutioniconapplied with advantage to; thewholly or'pr edominantly synthetic paper-machine felts, described in our copending centrates. During concentration, thesalt solution tends to localize-preferentially at the crossover, points of the fibres. As evaporation 'of the" water" continues, the salt.

solution ultimately becomes sufliciently concentrated to gelatinize small portions of the fibre surfaces at the cross over points, and on complete evaporation of the water, 7

the fibres ,become'bonded with adjacent fibres. There= after, therinorganic salt is washed out of the fabric with water. g 7

If a woven fabric forms as 'a paper-machine felt is composed of a mixture of two synthetic fibrous materlals While, in accordance with the present invention, .the synthetic fibres are bonded together at their mutual points of contacts, it should be remembered that it is extremely rare to find two fibres in a spunyarn which make'a line contact of appreciable length, although they may repeated lycross each other, so thatj the practice of thepresent process does not result: instiffening or reducing the normal flexibility of the felt to a degree such as to impair its utility for the intendedpurpose.

Moreover, the present fibre-bonding process can be reactant solution. Inother instances, it is preferred first to bond the fibres by impregnatiomevaporation of the entrained water. and 'rewa'shing and thereafter to raise one or. both surfaces. 'In this latter case, although theope r'an tion of. raising breaks some of the bonds onthesurface then a salt capable of swelling and dissolving or gelatinis ing the surface of both fibres is employed. For examples,

it the fabric is composed of nylon and Terylene, then calcium or magnesium thiocyanate is employed as the reactant,

. The concentration of inorganic salt in the impregnating liquor can be as low as 0.5% by weight, although for fibres, these fibres are still bonded below the raised surface,ian'd the fibres. of the yarns unaffected by raising are,

1 of course, stillbonded to oneianother. Ineitherlcase, the

nap fibres collectively "mask the weave pattern and provide a smooth surface. i I i In'ca'ses where -particularly, goodbonding isrrequired,

during the drying process following'impr'egnation,the

good fibre-to-fibrebonding, it ispreferredithat a 2 to;

5% solution is used, and the solution can, in fact, havea 7 concentration of inorganic reactant as high as 10% by eigh One example of the processing according to theinvent o i as tol ows a V a An endless woven fabric of a' structure suitable for use s a ra e -maeh n e a W aan rn i pun fabric can'be. pressed against the heated cylinder of the. felt-stretching machine by means of a relatively heavy roller...'

We claim: a a 1. The method of'making a woven fabric suitable for use as a papermakersfelt and 'whichpossesses wearfrom-crimped nylon staple" fibres. The fabric is treated at ambient temperature for 15 minutes in a 5% by weight solutions of lithium bromide, 4 gallons of solution being used for every 10, lb. of syntheticfibre. The impregnated Q fabric is hydro-extracted and then dried on a felt-stretchins machin a lea t e c linde -9 which i heated- E the water; evaporates from the felt, thus concentrating the lithium bromide, the latter ten'ds'to collect at the 'fibre crossovers, *gelatinisationof which results in'fibre-to-fibre bonding. When the fabric is completely dry, it is washed resistance such as resultsfr'omjtheincorporation therein of at least 'a predominance ofisynthetic fibrous material and which possesses;desirable characteristics of a conventional wool felt, including flexibility and permeability to watensaid method comprising the steps of providing woven fabric, of a structure acceptable for use as a base fab'ri cl'ofa papermakers feltand consisting, at least in .major proportion, of 'syntheticfibres, impregnating the fabric with a weak aqueous solution of inorganic salt, progre'ssively concentratin the salt soiutiomthe'reby intensiin water until free from lithium bromide, hydro-extracted,

and re-dried on the felt-stretching machine.

The aboveis only .onemethodof carry vention. Any conventional method of 'impr'egnationiand drying'can'be used and the. concentration and amount be variedwithout departing from the invention. 7

Furthermore,-

g V out; the in-J the fabric nee d'not necessarily be woven. wholly from spun synthetic yarns and, as'has been pointed? Qfying the normal tendency of thes'olution to migrateto I ward and accumulate at thep oints at which fibrescross and contact .one another,'1 whereby the concentrated. salt solution reacts with the fibresat saidcrossingpointafcaus'ing themto' geland coalesce andto"'forni perrn anentbonds predominantiy attlie fibre; crossing points, whereby the fabric retaih'san'acceptable percentage of its'inijtial waterpermeability and flexibility, then washing the fabric to remoye the salt, and thereafter drying the fabric.

: 2. flhe method according'toclaim ,1, wherein the initial concentration of the aqueous saltfsolution isibetween 2% and 10% by weight, 1

3. The method according to claim 1, wherein the inorganic salt is selected from the group consisting of calcium bromide and lithium bromide.

4. The method according to claim 1, wherein the inorganic salt is selected from the group consisting of calcium thiocyanate and magnesium thiocyanate.

5. The method according to claim 1, wherein the fabric consists, at least predominantly, of polyester synthetic fibres, and wherein the inorganic salt is selected from the group consisting of calcium thiocyanate and magnesium thiocyanate.

6. The method according to claim 5, wherein the fabric includes a substantial proportion of polyamide fibre.

7. The method according to claim 5, wherein the fabric comprises a substantial proportion of acrylic fibre.

8. The method according to claim 1, wherein the fabric is predominantly of polyamide fibre and the inorganic salt is selected from the group consisting of calcium bromide, lithium bromide, calcium thiocyanate and magnesium thiocyanate.

9. The method according to claim 1, wherein the fabric consists predominantly of acrylic fibre and the inorganic salt is selected from the group consisting of calcium bromide, lithium bromide, calcium thiocyanate and magnesium thiocyanate.

10. The method according to claim 1, further characterized in napping one side, at least, of the material after it has been dried.

11. The method according to claim 1, wherein one, at least, of the faces of the woven fabric is napped, prior to impregnation with the salt solution.

References Cited by the Examiner UNITED STATES PATENTS 2,255,890 9/41 Knowland 2873 2,332,373 10/43 Dorough et a1. 2873 2,365,931 12/44 Benger 281 2,389,120 11/45 Castellan 2873 2,392,842 1/46 Doell 57157 2,401,291 5/46 Smith 57140 2,460,674 2/49 Bihaly 2873 2,465,996 4/49 Bloch 281 2,771,659 11/56 Ball 2873 2,811,029 10/57 Conner 28--73 2,903,021 9/59 Holden et a1 139-426 DONALD W. PARKER, Primary Examiner.

MERVIN STEIN, Examiner. 

1. THE METHOD OF MAKING A WOVEN FABRIC SUITABLE FOR USE AS A PAPERMAKER''S FELT AND WHICH POSSESS WEARRESISTANCE SUCH AS RESULTS FROM THE INCORPORATION THEREIN OF AT LEAST A PREDOMINANCE OF SYNTHETIC FIBROUS MATERIAL AND WHICH POSSESS DESIRABLE CHARACTERISTICS OF A CONVENTIONAL WHOOL FELT, INCLUDING FLEXIBILITY AND PERMEABILITY TO WATER, SAID METHOD COMPRISING THE STEPS OF PROVIDING WOVEN FABRIC, OF A STRUCTURE ACCEPTABLE FOR USE AS A BASE FABRIC OF A PAPERMAKER''S FELT AND CONSISTING, AT LEAST IN MAJOR PROPORTION, OF SYNTHETIC FIBRES, IMPREGNATING THE FABRIC WITH A WEAK AQUEOUS SOLUTION OF INORGANIC SALT, PROGRESSIVELY CONCENTRATING THE SALT SOLUTION, THEREBY INTENSIFYING THE NORMAL TENDENCY OF THE SOLUTION TO MIGRATE TOWARD AND ACCUMULATE AT THE POINTS AT WHICH FIBRES CROSS AND CONTACT ONE ANOTHER, WHEREBY THE CONCENTRATED SALT SOLUTION REACTS WITH THE FIBRES AT SAID CROSSING POINTS, CAUSING THEM TO GEL AND COALESCE AND TO FORM PERMANENT BONDS PREDOMINANTLY AT THE FIBRE CROSSING POINTS, WHEREBY THE FABRIC RETAINS AN ACCEPTABLE PERCENTAGE OF ITS INITIAL WATERPERMEABILITY AND FLEXIBILITY, THEN WASHING THE FABRIC TO REMOVE THE SALT, AND THEREAFTER DRYING THE FABRIC. 